<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<body>
	</body>
	<script type="text/javascript">
		var obj={
			
		}
		
		Object.defineProperty(obj,"a",{
			get:function(){
				console.log(this)
				return this._a_;
			},
			set:function(val){
				console.log(this)
				this._a_ = val;
			}
		})
		
		obj.a=4;
		console.log(obj.a);
		
		
//		var result =Object.getOwnPropertyDescriptor(obj,"a");
//		console.log(result);
	</script>
</html>